At a base near the naval port of Sevastopol, an air force commander takes to YouTube to appeal for clear orders of engagement with the Russian forces who have occupied much of his base. In a naval base near regional capital Simferopol, a commander reports feeling like a hostage, and fearing what will come in the next few days.

On the eve of Sunday's referendum on whether the Black Sea peninsula should break away from Ukraine and join Russia, Crimeans of all ethnicities waited with deepening anguish and fear about the vote that at best, will yield months or years of uncertainty, and at worst, will spark war.

Among those facing the greatest and most fraught uncertainty were Ukraine's military forces on the peninsula, who have been hemmed in by heavily armed Russian troops and warned by the region's pro-Russian leader that they would be considered "illegal" if they didn't surrender.

With the new government in Kiev struggling to respond to a threatened Russian invasion in the east, build international support and stave off economic disaster, soldiers and sailors have lamented openly that they don't know what they're supposed to be doing. And, more importantly, what they're going to do if shooting breaks out.

Russia effectively took control of Crimea, where it has a large naval base, late last month after Moscow-friendly President Viktor Yanukovych fled the country in the wake of months of protests. The Kremlin says he was the victim of a coup and refuses to recognize the authorities who took over.

The head of Crimea's unrecognized Russian-backed government, Sergei Aksyonov, has said Ukrainian solders will be allowed to surrender peacefully, leave Crimea altogether or resign from the armed forces.

In a message on Twitter, he warned that Ukrainian units that refuse to swear allegiance to the new Crimean authorities after Sunday's referendum would be considered "illegal armed formations."

Ukrainian officials have said more than 20,000 Russian troops are in Crimea. Many are believed to be under the command of the Black Sea Fleet, which is based in Sevastopol under a lease deal with Ukraine.

Against this backdrop, Ukraine's outmatched armed forces have been stuck in the middle, harassed and blockaded in bases by masked gunmen and Russian soldiers wearing no identifying emblems, but often driving military trucks bearing Russian license plates. Ukrainian officers and servicemen have complained about not only being outgunned, but also about having no clear direction or orders from Kiev, where a new government is struggling to take shape and to respond to the Russian threats.

In the video made earlier this week, Col. Yuly Mamchur of the 204th Tactical Aviation Brigade sits with four other officers and appeals for direction from his commanders: the Belbek military airfield he commands is under pressure from Russian forces that have cordoned it off, and he fears his men may have to start shooting.

"Each day, we receive ultimatums of an increasingly harsh nature from the armed forces of the Russian Federation. In the interest of averting the possibility of armed clashes I appeal to you in the nearest possible term to issue clear instructions to commanders," Mamchur says in the video posted to YouTube. "If no such corresponding order is issued, we will be forced to act under the general orders of the Ukrainian armed forces and open fire. We are ready to fulfill our orders to the very end."

The video appeal by Mamchur was echoed Friday by a group of senior generals, including several former defense ministers, who released an open letter to Russian President Vladimir Putin to withdraw Russian forces from Ukraine.

"Morally, Ukrainian soldiers are not yet ready to fire at Russian soldiers. Further escalation of unlawful actions of Russian troops in Crimea may change this situation drastically," the letter said. "The mothers of our soldiers will never forgive us if the blood of their sons is spilled."

A spokesman for the Ukrainian military in Crimea, Vladislav Seleznyov, said witnesses in the eastern port of Kerch, which is separated from Russia by the narrow Straits of Kerch, had seen more than a dozen S-300 surface-to-air missile launchers at the railway station. Ukrainian social media sites are crowded with photos and video of Russian artillery being moved along Crimean roads and Russian radar stations being erected on hilltops.

On the approach to the base's main gates, a regiment of heavily armed, masked soldiers stood guard in the trees and on the shoulders of the road about every 100 feet. More than a dozen trucks and motorized vehicles were parked, one bearing a license plate indicating it was from the Moscow region. About 50 feet (15 meters) from the main gate, two masked Russian soldiers blocked the road, with a GAZ-2330 Tiger armored vehicle nearby.

The base's rear gates were lightly defended, locked with a simple padlock. An armored vehicle stood inside, but civilians and soldiers walked in and out and sentry guards, mostly unarmed, laughed and joked with one another. Some soldiers came out to receive bags of food from relatives, while others carried out garbage. One officer came out to stroll with his young daughter, while his wife pushed a tricycle.

Base officers, who requested anonymity because they weren't authorized to speak with the media, said commanders talk regularly with their Russian counterparts, and they regularly allow the Russians to use the base's wash facilities for soldiers to shower and shave. One Ukrainian officer said he and his colleagues are worried what will happen to them after Sunday's vote.

In addition to the masked Russian soldiers outside the main gate, a motley group of "self-defense" volunteers, dressed in civilian clothing, stood around chatting, listening to radio music, chopping wood for a barrel fire and drinking tea. With an old amusement park train painted in faded colors and reading "The Magical Valley of the Red Caves" on its side serving as a partial roadblock, the encampment had the feel of a weekend camping trip.

Andrei Karavulov, a 48-year-old retired lieutenant colonel overseeing the civilian sentries, said the group was defending the base from "provocations from radical citizens who are coming here trying to scare us with accusations of criminal allegations of separatism" and compared Sunday's vote with the U.S. Declaration of Independence of 1776. He said the armed servicemen digging in nearby were all from the Russian Black Sea fleet forces.

"It's absolutely quiet here, absolutely calm. There are no problems. People walk around doing their thing, taking showers, bathing. There are absolutely no problems here whatsoever," Karavulov said. "We are all waiting for the results of Sunday, the referendum, and then all will be normal."

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